Conventional high-frequency antennas are often cumbersome to manufacture. For example, antennas designed for 100 GHz bandwidths typically use machined waveguides as feed structures, requiring expensive micro-machining and hand-tuning. Not only are these structures difficult and expensive to manufacture, they are also incompatible with integration to standard semiconductor processes.
As is the case with individual conventional high-frequency antennas, beam-forming arrays of such antennas are also generally difficult and expensive to manufacture. Conventional beam-forming arrays require complicated feed structures and phase-shifters that are incompatible with a semiconductor-based design. In addition, conventional beam-forming arrays become incompatible with digital signal processing techniques as the operating frequency is increased. For example, at the higher data rates enabled by high frequency operation, multipath fading and cross-interference becomes a serious issue. Adaptive beam forming techniques are known to combat these problems. But adaptive beam forming for transmission at 10 GHz or higher frequencies requires massively parallel utilization of A/D and D/A converters.
To address these problems, injection locking and phase-locked loop techniques have been developed for an array of integrated antenna oscillator elements as disclosed in U.S. Ser. No. 10/423,160, (the '160 application) the contents of which are hereby incorporated by reference in their entirety. The '160 application discloses an array of integrated antenna elements, wherein each antenna element includes a phase-locked loop (PLL) that uses the antenna as a resonator and load for a voltage-controlled oscillator (VCO) within the PLL. The VCOs within each antenna element are slaved to a common reference clock that is distributed using phase adjustment circuitry rather than a traditional corporate feed network. The phase of each VCO can be changed relative to the reference clock by adjusting the VCO's tuning voltage such that some or all of the antenna elements become injection locked to each other. Although injection locking provides an efficient beam steering technique, a need in the art exists for improved techniques of actively phasing such antenna elements to provide a desired beam direction.